1. Field of the Invention
The present invention relates to a transmitted-picture quality monitoring apparatus and more particularly, to a transmitted-picture quality monitoring apparatus for monitoring the transmitted-picture quality on a transmission chain from a remote place by extracting the picture quality characteristic amount at each point on the transmission link and comparing the extracted picture quality characteristic amount.
2. Description of the Related Art
When monitoring a transmitted-picture quality on a transmission link comprising transmission chain, the picture quality characteristic amount at any point on the transmission link are extracted, and the extracted picture quality characteristic amount are transmitted to a central monitoring room and compared so as to monitor remotely the transmitted-picture quality on a transmission link in batch.
The inventors et al. have proposed a transmitted-picture quality monitoring apparatus for monitoring the transmitted-picture quality on a transmission link in patent documents 1 and 2. According to this transmitted-picture quality monitoring apparatus, a picture is divided into blocks with a certain size, an arbitrary transform coefficient is extracted from transform coefficients obtained by orthogonal transform of the picture of each block, and is transmitted to a central monitoring room as a picture quantity characteristic amount. This transmitted-picture quality monitoring apparatus exerts its effect especially when as described in the patent documents 1 and 2, spectrum spreading is applied to the picture and then that picture is orthogonally transformed and the transform coefficient is extracted and transmitted. The spread spectrum is realized by randomly changing the sign of each pixel constituting the picture.
Patent document 1: Japanese Patent Application Laid-Open No. 2003-009186
Patent document 2: Japanese Patent Application Laid-Open No. 2003-087823
In the inventions proposed in the above-described patent documents 1 and 2, the transform coefficients obtained by orthogonal transform are randomized, that is, a spectrum is randomized by the spectrum spreading in order to enhance a tendency for the transform coefficient arbitrarily extracted to represent the whole picture from a statistical view. Thereby, the picture quality characteristic amount can be transmitted to the central monitoring room, using a low-speed transmission link and at the same time, a transmitted-picture quality can be monitored with high accuracy.